Knife sharpener



Dec' 16, 1947-.

L. M. MCBRIDE 2,432,535

KNIFE SHARPENER Filed Aug. 13' 1945 2 Sh6ets sheet l "I Il'll Dec; 16, 1947. L. M. McBRlDE 2,432,535

KNIFE SHARPENER 4 Filed Aug. 13, 1945 2 Sheets-Sheet 2 INVENTOR. Ew/.r M. M S BRIDE Eg @yw Patented Dec. 16, 1947 UNITED STATES PATENT OFFICE KNIFE SHARPEN Lewis M. McBride, Arcadia, Calif. Application August 13, 1945, Serial No. 610,477.44

11 Claims.

Thisinvention is concerned with knife sharpening and provides improved guard and guiding means for"V knife Sharpeners, particularly those ofthe type having overlapping wheels mounted on spaced axes that extend' in the same general direction, the knife being sharpened by drawing its edge across the peripheries of the Wheels in the' direction of the axes.

ThisA application is. a continuation-in-part ofy my co-pending application Serial No. 560,229, filed October 25, 1944.

The parent application discloses an improved knife Sharpener comprising a plurality of grinding wheels" mounted respectively upon substantially parallel axes with thewheels overlapping. Preferably the wheels are arranged in sets with several wheels' mounted'on each axis, interposed between and overlapping a like' set of wheels mounted on the other axis. The knife is sharpened by having itsv edge drawn lengthwise between the rotatingwheels with its edge in contact with both sets and with its flat so held that the Wheels produce a symmetrical bevel of proper degree on both sides ofthe blade.

Thewheels are designed to' be motor driven at relatively high speed, i. e; at peripheral speeds in excess of 1500 feet perminute and preferably at 350D-4000 feet per minute, with the wheels on each side' turnin'goppositely to those on the other side but directly toward the' knife edge from the overlapped portions of the wheels.

In accordance With the present invention, ap paratusof the foregoing general type is provided with a resilient guard and a knife guide is formed of opposed plates between which the blade is tted. The plates of' the knife guide are mounted on the guard, and the resiliency of the latter presses the plates toward each other so as to hold the blade in proper position for grinding.

Since the guide-guard combinationv may be used with a variety of grinding' wheel arrange-V ments in addition to the type described above, my invention contemplates, in a knife Sharpener having atleast one grinding Wheel, the combination- Whi'ch comprises a guide adapted to hold a knife withitsedge incontact with the grinding Wheel and: formed of members having opposed surfaces between which the flat of the knife is held, and a guard encasing' the peripheries of the wheel arid having a gap' or slit, with the guideni'embersfastened to. the guard respec- Y 2 tively on opposite sides of the slit, the guide being resilient (i. e. springy) so as to press the guide members towardeach other and hold the blades in correct grinding position. Y

In my preferred structure the guard is fastened to a base extending parallel to the axes of the Wheels, and is in two halves which are mirror images of each other. Each half adjacent the base has a flat plate section which is topped by an integrally formed plate section that curves over the grinding medium toward the curved section of the other half- The guides are plates formed integrally with the respective curved sections. In effect then, one guard half and one guide half are formed integrally, and the combined guide-guard fulfills the multiple functions of compressing and guiding the blade, guarding the operator and collecting the dust formed in grinding,

The Wheels in my preferred for'in of knife grinder are motor-driven through a gear train, and I prefer to place` the motor and the gear train in addition to the wheels within the guard members, thus providing a compact safe structure of neat and esthetic form.

I have discovered that substantially all the steel cut from the knives by grinding wheels may be collected by means of a horseshoe magnet, preferably a permanent one, placed with respective legs (poles) extending parallel to the wheel axes on opposite sides of the wheelsv and' Within the guard, and have' developed a convenient means for detachably mounting the magnet in this position. I have found that the great proportion of the dust produced with my Sharpener is magnetic, since the amount abraded from the Wheels themselves is' relatively small. Hence the magnet collects most (say of the dust, to the end that the interior of the apparatus need be cleaned only at very long intervals.

These and other features of my invention will be understood more thoroughly in the light of the following detailed description, taken in conjunction with the drawing, in which:

Fig. 1 is a perspective view of apreferred form of the knife Sharpener of my invention with one guide-guard-half removed;

Fig. 2 is a perspective View of the guide-guard-A ha-lf removed from the apparatus of Fig. l;

Fig. 3 is a plan viewof the Sharpener of Fig'. 1 with part of the guard4 broken awa Fig. 4 is an elevation of the apparatus of Fig. 3 with one guide-guard-half removed;

Fig. 5 is a motor end view of the apparatus of Fig. 3;

Fig. 6 is a gear box endview of the apparatus of Fig. 3;

Fig. 7 illustrates the manner in which the guard-halves of Fig. 3 are attached to the base of the apparatus;

Fig. 8 is a perspective view of the magnet of the apparatus of Fig. 3; and

Fig. 9 is a perspective view of a modified form of my sharpener in which the knife guide projects above the case or guard.

Referring to the drawings, the apparatus comprises in essence, a motor l of conventional design mounted on a rectangular base Il having rounded corners. A transmission or gear box l2 is connected to one end of the motor and has two upper branches, each of which carries a spindle i3, ill upon which sets of grinding wheels l5, I6 are mounted. The motor, the gear box, and grinding wheels are encased in a combined guard and knife guide I1 fastened to the base. Magnetic dust formed in the operation of the apparatus is collected on a magnet I8 disposed inside the case adjacent the wheels.

Considering the structure in greater detail, it will be observed that it is substantially symmetrical (see Figs. 3, and 6). The motor, which conveniently is of le or 1/0 horsepower, is mounted toward one end of the base with its shaft extending longitudinally of the base. The gear boX or transmission is fastened to it adjacent the other end. cantilever fashion, in bearings in the top of the gear box and the spindles extend symmetrically over the motor parallel to its shaft. The combined guard and knife guide is composed of two sections I9, 20 which are mirror images of each other. Each section comprises a lower plate portion (fastened at the side of the base by means of an angle 2l), an upper portion which curves inwardly over one set of grinding wheels, and a downwardly projecting guide portion 22, 23 which passes between the grinding wheels and is slotted or notched on its lower edge to permit this (sce Fig. 2).

Conveniently, there are six grinding wheels on each spindle and these are separated from each other by bushings or spacers 24 that are slightly thicker than the wheels themselves to permit clearance between the Wheels which overlap. One set of grinding wheels overlaps the other set by an angle (which may range from 20 to 50 but preferably is about 42), with the wheels of one set interposed between those of the other set. The angle of overlap is shown on Fig. 6.

By means of gears (not shown) within the gear box, the two spindles are turned opposite to each other, directly from the area of overlap toward the knife edge: see Fig. 6.

The combined guide and guard members are resilient so that the two guide plates tend to spring apart when a knife blade 25 (see Fig. 6) is inserted between them. Since the guide plates are symmetrically disposed, the knife blade is centered in a vertical position and may be drawn longitudinally through the guides with the blade in contact with the peripheries of all twelve grinding wheels. In this manner, a sharpened edge with a proper and uniform symmetrical bevel is automatically produced.

The grinding wheels and spacers are keyed on lThe two spindles are supported,A

their respective spindles and held thereon by means of nuts threaded on the ends of the spindles.

As indicated hereinabove, magnetic dust formed in grinding the knife blade (and this comprises more than 80% of the total dust formed, for the grinding wheels are much harder than the knife and are abraded very slightly) is collected by means of the magnet which is detachably mounted within the guard or case by means of clips 2B, 2'! fastened to the motor at the end opposite the gear case. Preferably the magnet is of the permanent type so that it is continuously magnetized. It may be in the form of an Alnico strip having a handle threaded into it at the center and with two soft iron pole pieces riveted or otherwise fastened at its ends. The soft iron pole pieces project respectively on the outside of each set of grinding wheels just below the center line of the spindles.

` Means such as wires 32 for energizing the motor areA provided and conveniently project from the apparatus adjacent the base on the end remote from the gear box.

The motor should be of such speed that the peripheral speed of the wheels is from 3500 to 4000 feet per minute. Slower peripheral speeds may be employed, though speeds below 1500 feet per minute are not recommended.

Conveniently the two guard-halves are stamped from sheet metal that is spring'y or resilient in character and also has relatively high heat conductivity. When the knife blade is removed, the guard-halves spring together so that the gap between the guide members or plates is substantially closed (see Fig. 5). When the knife is inserted between the guide plates, the guard-halves spring apart, but the plates are compressed against the at of the knife and hold it in a symmetrical position proper for sharpening and for conduction and dissipation by the guard halves of the heat developed in grinding. With the wheels turning, the knife blade is drawn longitudinally through the apparatus in contact with the periphery of all the wheels and is immediately sharpened to the correct bevel.

If desired, the guiding wheels and bushings of each spindle may be formed integrally, though I prefer to employ simple grinding disks with metallic or plastic bushings in between.

Figs. 2 and 7 show the manner in which the guard-halves are amxed t0 the base. Thus, the angle 2| is riveted inside the guard-half and its lower branch is forked or slotted. A bolt 33 passing through the base and holding the motor thereto also passes through the slot in the angle and upon tightening holds the guard-half securely in position. By loosening the bolt slightly, the guard-half may be withdrawn when the apparatus is to be cleaned.

Wheels made of various types of abrasives may be employed depending on the coarseness of grinding desired.

A modified form of the invention is illustrated in Fig. 9 in which the guide plates 40, 4l instead of projecting downward from the guard-halves, are bent upwardly and form vertical ns along the top of the guard. This type of guide is satisfactory when wide-bladed knives, etc. are to be sharpened, but the downwardly projecting guide plates slotted to t between the grinding wheels are preferred since they guide a blade, particularly a narrow blade, more accurately.

The apparatus of my invention may be operated in a horizontal position or fastened on a wall aaa-atea 5, to operate vertically. In either case, substantially all! off the dust willbe collected' by themagnet, probablybecause the dustis concentrateoli inthe neighborhood of the magnetl by the rotating wheels and the. defiectingV action of the guard halves. Thus' the combination guard-guide serves` a; variety of functions. It protects; the; operatorI and also protectsithewheels from damage from; exterior. sources.. At thel same1time;,the guanrd-guideb collects, abrasive; dust. particlesa and throws magnetic dust particles toward the magnet where they are recovered. Lastly, the guardguide assures that the blade will be held in proper position for grinding and inhibits loss of temper of the blade. Thus, if the guard-guide is made of metal or other material having high heat conductivity, the heat of grinding is rapidly conducted away from the knife to the guide plates, thence into the guard-halves and there conducted into the base of the motor.

The apparatus of my invention in its preferred form is a very compact device of esthetic appearance. It may be used with entire safety, in households, restaurants, and the like, with the assurance that knives will be sharpened without loss of temper and without glazing or loading of the grinding wheels.

The magnet may be easily removed from the apparatus without removing the guard whenever sufficient dust particles have accumulated. Occasionally, but only at very infrequent intervals, it may be desirable to remove one or both guardhalves and wipe dust from interior surfaces of the apparatus. Preferably, both motor and gears are totally enclosed, so as to be dust proof.

The apparatus may be used to grind various types of knives. Irrespective of the original type of knife edge, all knives may be sharpened satisfactorily with the apparatus of the invention, even those such as bread knives which are provided with a saw-tooth edge.

I claim:

1. In a knife Sharpener provided with a plurality of overlapping grinding wheels mounted on axes spaced from each other and extending in the same general direction and a base upon which the wheels are mounted, the combination which comprises a guide adapted to hold a knife with its edge in contact with the peripheries of the wheels and its flat extending transverse to the line joining the axes and composed of opposed plates between which the flat of the knife is slidable, a guard mounted on the base and substantially enclosing the edges of the wheels and having a slit therein parallel to the guide members with the guide members fastened to the guard respectively on opposite sides of the slit, the guard being resilient so as to press the guide members toward each other.

2. Apparatus according to claim 1 in which the guide members project outwardly from the guard.

3. In a knife Sharpener provided with a plurality of sets of overlapping grinding wheels mounted on axes spaced from each other and extending in the same general direction and a base upon which the wheels are mounted, the combination which comprises a guide adapted to hold a knife with its edge in contact with the peripheries of the wheels and its fiat extending transverse to the line joining the axes and composed of opposed plates between which the flat of the knife is slidable, a guard mounted on the base and substantially enclosing the edges of the wheels and having a slit therein parallel to the guide 6 members: Witlm the guide members fastenedtothe guard respectiveliyion opposite sides; off the slit and projecting inwardly towardV the wheels; the guardibeing-'resiiient so as to press the guide members toward each other.

4. Apparatus according-to claim 3 in which the free edges-off the guidemembersarenotched to fit between the overlapping sets of. wheels:v

5. In a. knife. Sharpener provided` with a plurality of overlapping grinding wheels mounted on axesispaced from each otherY and extendingfinthe same. general directionand abase upon whichithe wheels are mounted, the combination which comprises a guide adapted to hold a knife with its edge in contact with the peripheries of the wheels r and its at extending transverse to the line joining the axes and composed of opposed plates between which the at of the knife is slidable, a guard mounted on the base and substantially enclosing the edges of the wheels and having a slit therein parallel to the guide members with the guide members fastened to the guard respectively on opposite sides of the slit, the guard being resilient so as to press the guide members toward each other, and a horseshoe type magnet disposed within the guard with its poles extending in the direction of the wheel axes on opposite sides of the group of Wheels.

6. Apparatus according to claim 5 in which the magnet is permanent and its pole pieces are soft iron.

7. In a knife Sharpener having a plurality of overlapping grinding wheels mounted with parallel spaced axes on a base and adapted to grind a knife disposed with its flat extending in the direction of the axes and transverse to a line connecting them, with the edge of the knife in contact with the wheel peripheries, the combination which comprises a guide means comprising opposed flat-sided members adapted to press against opposite sides of a knife inserted between them in grinding position, and a combined guard and dust collector comprising guard pieces that are substantially mirror images of each other disposed around the peripheries of the wheels and attached to the base and to the respective members, the guard members being resilient so as to compress the guides together.

8. In a knife Sharpener provided with at least one grinding wheel mounted on a base, the combination which comprises a guide adapted to hold a knife with its edge in contact with the grinding wheel and formed of two members having opposed surfaces between which the flat of the knife is held, the space between the opposed surfaces being open at the end to permit the knife blade to be drawn longitudinally between the surfaces, and a guard disposed around the periphery of the wheel and composed of two sections each mounted rigidly on the base and connected respectively rigidly to a guide member, at least one guard section -being springy in a direction transverse to the major surfaces of the guide members and acting to press the guide members toward each other when the knife blade is inserted between them.

9. Apparatus according to claim 8 in which each guard section is formed integrally with the guide member to which it is attached.

10. Apparatus according to claim 8 in which the guard section and the attached guide member on each side are formed integrally in a substantial mirror image of the guard section and attached guide member on the other side.

11. Apparatus according to claim 8 provided with a magnet disposed Within the guard adjacent Number the Wheel and adapted to collect magnetic mate- 1,925,108 rial ground off the knife blade by the Wheel. 2,228,385 LEWIS M. MCBRIDE. 1,836,064

5 REFERENCES CITED n The following references are of record in the Number file of this patent: 2 .0

UNITED STATES PATENTS 10 661,652 Number Name Date 654,215 Worden July 24, 1900 Name Date Nagy Sept. 5, 1933 Burns Jan. 14, 1941 Boche Dec. 15, 1931 FOREIGN PATENTS Country Date Great Britain July 17, 1939 Italy Oct. 2, 1931 France Mar. 11, 1929 

